Easily-openable packaging container having notched inner surface layer

ABSTRACT

A multilayer container having a flange portion and an easily-openable packaging container packaged by using said multilayer container, wherein the interlaminar strength of said multilayer container is smaller than the peeling strength between said flange portion and the lid member, and a ring notch is provided to an inner surface layer of the flange portion inside a heat sealed portion. 
     The packaging container has both a good sealing property and an easy openability and has an excellent resistance to boiling and retort treatment, and 9 peeled surface having a good appearance. 
     A method for producing said multilayer container and a method for producing said packaging container, and an apparatus to be used for producing said multilayer container, and a method for filling and packaging, and an apparatus for filling and packaging are disclosed.

This application is a continuation of application Ser. No. 036,014,filed Apr. 8, 1987.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a multilayer container and a method forproducing the multilayer container, an easily-openable packagingcontainer packaged by using the multilayer container, a method forpackaging an article by using the multilayer container, and an apparatusfor packaging an article (e.g. foods and drinks). More precisely, thepresent invention relates to a multilayer container suitable for heatsterilization packaging, which makes the setting of the heat sealingcondition at heat sealing of a lid member easy. This invention is ableto make a package which has not only an excellent sealing property butalso easy openability and which can be opened with a stable openingforce, a method and an apparatus for easily producing the multilayercontainer, an easily-openable packaging container packaged by using theabove-mentioned multilayer container which provides a peeled surfacehaving a good appearance and has an excellent resistance to boiling andretort treatment, a method for packaging, and an apparatus for packagingeasily.

(2) Description of the Prior Art

Heretofore, flanged containers have been largely used for packagingfoodstuffs or the like, and the container is sealed by heat sealing alid member thereto after a content is filled therein. The heat sealcontainer thus formed, however, is defective in that, if the sealingproperty is improved by increasing the heat seal strength, theopenability at the time when the content is used is aggravated,resulting in the necessity for opening operation using an edged tool orthe like, and, on the other hand, if a material having a properinterlaminer strength is selected to improve the openability, since thesealing property varies broadly depending on the heat seal conditions,such as temperature, pressure, and time, or owing to matters such as thecontent sandwiched between the heat seal surfaces, a uniforminterlaminer strength cannot be obtained resulting in a decreasedsealing property. Therefore, it cannot be used for a package in whichthe internal pressure is increased by heat sterilization such as boilingand retort treatment.

However, the traditional notion for the easy openability was limited tothe openability in a peeling opening from the sealing area where a lidmember and the flange portion of a container were heat sealed.Therefore, it has been proposed to decrease the heat seal property ofthe heat sealing layers. However, in this method, a good heat sealingproperty and an easy openability are incompatible and the appearance ofthe peeled surface is deteriorated (e.g. nap or thread) resulting in adecreased commercial value. Therefore, it cannot bring a substantialsolution.

Heretofore, as the apparatus for forming a notch in the flange portionof a container, there is known an apparatus for forming a score forvending-cut in one lower portion of the flange portion of a container inorder to improve the openability of a lid member (c.f. Japanese UtilityModel Publication No. 48102/1983). The apparatus is composed of a heatblade capable of ascent and descent for forming a notch on the undersideof a flange portion and a cooling bed for supporting the flange portion.

However, though such an apparatus can form a notch for cutting a flangealong a straight line on a portion of the flange portion, accuracy ofthe depth or location of the notch is not always required of theapparatus according to the object of the apparatus, and, therefore, itis not satisfactory in the accuracy of the notch.

SUMMARY OF THE INVENTION

The primary object of the present invention is to provide a multilayercontainer, which can be advantageously used for a packaging containerheat sealed with a lid member which is to be opened by taking advantageof the delamination of the multilayer container instead of by using theheat sealed area of the multilayer container and the lid member as apeeling area, can be easily opened with a stable opening force, has anexcellent sealing property since it can be tightly sealed with a lidmember leaving the peelability out of consideration, and further has aresistance to boiling or retort treatment, and to provide a method forproducing the multilayer container

Another object of the present invention is to provide theabove-mentioned packaging container having an excellent openability andsealing property in which an article is filled in the said multilayercontainer and to provide a method for filling-packaging.

Another object of the present invention is to provide an apparatus forproducing the above-mentioned multilayer container and an apparatus tobe used for the above-mentioned method for filling-packaging.

The multilayer container of the present invention is a multilayercontainer having a flange portion, in which, a notch is provided at aninner peripheral portion of said flange portion of the multilayercontainer which can be delaminated between an inner surface layer and alayer contacting thereto, said notch being capable of cutting the innersurface layer at the inner peripheral portion of said flange portion atthe time when the inner surface layer is peeled. Such a multilayercontainer can be produced by forming a notch by means of pressing with anotching blade, pressing with a heating blade, cutting with a cuttingedge, a heating means, or a combination thereof at an inner peripheralportion of the flange portion of a multilayer container which can bedelaminated between an inner surface layer and a layer contactingthereto, said notch being capable of cutting the inner surface layer atthe inner peripheral portion of the flange portion at the time when theinner surface layer is peeled.

Also, such a multilayer container can be produced dimensionallyaccurately by a method for producing a flanged container comprisingheating a multilayer sheet composed of thermoplastic resins andthermoforming, in which a notch is formed in the container forming stagewith a ring notching blade.

Further, an apparatus of the present invention for forming a ring notchin the flange portion of a container comprises (a) a ring blade equippedwith a heating means for forming a ring notch at the inner surface layerof the flange portion of the multilayer container and (b) a supportingmember having a container receiving portion for supporting the flangeportion at forming of a notch, at least one of (a) and (b) being capableof ascent and descent and being secured to the apparatus proper throughan elastic member, and the apparatus can form a notch on a multilayercontainer dimensionally accurately.

The easily-openable packaging container of the present invention is apackaging container comprising a multilayer container having a flangeportion and a lid member heat sealed at the flange portion, in which theinterlaminer strength of said multilayer container is smaller than thepeeling strength between said flange portion and said lid member, and aring notch is provided to an inner surface layer of said flange portioninside a heat seal portion, and has both of a good sealing property andan easy openability.

The method for filling and packaging an article of the present inventionis an packaging method comprising filling an article in a container andheat-sealing a lid member to the flange portion of the said container,in which a container of a multilayer structure able to be delaminated isused as the said container, a notch is provided to an inner surfacelayer of the said container at a peripheral portion of the flangeportion inside a heat seal portion before or after an article is filled,and a lid member is heat sealed. The apparatus for filling and packagingan article of the present invention comprises (a) an article fillingmeans for filling an article in a container made of a multilayer sheetable to be delaminated, (b) a notch forming means for providing a notchto an inner surface layer of a flange portion inside a heat seal portionof the flange portion of the container and a lid member before or afterthe article is filled, (c) a lid heat sealing means for heat sealing alid member to the flange portion of said container, and (d) a punchingmeans for punching the peripheral portion of the heat seal portion. Bythe use of the above-mentioned method for filling and packaging and thisapparatus for filling and packaging, a packaging container having bothof a good sealing property and an easy openability can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing a structure of a multilayer containerof an embodiment according to the present invention.

FIG. 2 is a sectional view of a container in which the multilayercontainer shown in FIG. 1 is heat sealed with a lid member.

FIG. 3 is a sectional view of a multilayer container of anotherembodiment of the present invention.

FIG. 4a, FIG. 4b, FIG. 4c, FIG. 4d, and FIG. 4e are each an explanatoryviews showing the method for forming a notch.

FIG. 5 is a process view showing a process for producing a multilayercontainer of an embodiment according to the present invention.

FIG. 6 is a partially sectional view of an example of a forming sectionof the process drawing shown in FIG, 5.

FIG. 7 and FIG. 8 are each a schematic sectional view of an apparatusfor forming a notch of different embodiment according to the presentinvention.

FIGS. 9(A), (B), (C), (D), (E), (F), and (G) are each an explanatoryview illustrating form of blade edge of a ring blade.

FIG. 10 is a sectional view showing the form of a notch formed by theblade edge shown in FIG. 9(G).

FIG. 11 is an explanatory view illustrating a state wherein a pluralityof multilayer containers are formed in one sheet.

FIG. 12 is a partially sectional view of an easily-openable packagingcontainer of an embodiment according to the present invention.

FIG. 13 is a partially sectional view of an easily-openable packagingcontainer of another embodiment according to the present invention.

FIG. 14 through FIG. 16 are partially sectional views of easily-openablepackaging containers of other embodiments according to the presentinvention.

FIG. 17a is a partially sectional view of an easily-openable packagingcontainer of an embodiment according to the present invention and FIG.17b is a partially sectional view illustrating a state wherein the lidmember of the easily-openable packaging container shown in FIG. 17a isbeing peeled.

FIG. 18a and FIG. 18b are explanatory sectional views illustrating anexample of operation for forming a notch on a multilayer container.

FIG. 19 and FIG. 20 are each a perspective view of a multilayercontainer of an embodiment according to the present invention, and

FIG. 21 and FIG. 22 are partially sectional views of easily-openablepackaging containers wherein the multilayer containers shown in FIG. 19and FIG. 20 are heat sealed with lid member.

FIG. 23 is a partially sectional view of an easily-openable packagingcontainer of an embodiment according to the present invention, and

FIG. 24 is a partially sectional view illustrating a state wherein theeasily-openable packaging container shown in FIG. 23 is being opened.

FIG. 25 is a sectional view of an example of a lid member to be used inthe present invention.

FIG. 26 is an explanatory view illustrating an apparatus for filling andpackaging an article of an embodiment according to the presentinvention.

FIG. 27 is a partially sectional view of an example of aneasily-openable packaging container of the present invention.

FIG. 28 is a sectional view of a test piece for measuring the peelingstrength of a packaging container.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a sectional view of a multilayer container of an embodimentaccording the present invention. A reference numeral 1 represents aninner surface layer of the multilayer container, a reference numeral 2represents a layer contacting thereto, and a reference numeral 3represents a notch formed at the inner peripheral portion of a flangeportion. A reference numeral 4 represents a flange portion, which is tobe used for heat-sealing the inner surface layer 1 of the multilayercontainer and a lid member after an article is filled and a lid memberis covered.

The shape of the multilayer container of the present invention is notcritical, and it is usually circular, square, and so forth, and themultilayer container is heat-sealed circularly along a flange portion ofthe shape. Also, the multilayer container may be cup-shaped ortray-shaped.

Referring to the multilayer structure of the multilayer container, it isnot critical so long as the interlaminer strength of the multilayercontainer is smaller than the heat seal strength of a lid member and themultilayer container so that delamination occurs between the layers ofthe multilayer container at peeling of the lid member, and the lidmember can be easily opened. The preferable interlaminer strength of themultilayer container is from 200 to 1500 g/15 mm, more preferably from300 to 1200 g/15 mm (tensile speed: 300 mm/min). Further, the thicknessof the inner surface layer at the flange portion is usually from 5 to150 μm, preferably from 10 to 100 μm.

Such a multilayer container is not critical so long as it has amultilayer structure composed of such combination of resins or resinsand other materials that a proper interlaminer strength is obtained.Illustrative of suitable resin are polyolefin base resins, polystyrenebase resins, polyamide base resins, polyester base resins, polycarbonatebase resins, and the like, a mixture thereof, or a mixture thereof inwhich from 5 to 70% by weight of various elastomers and variousadditives or inorganic fillers are further mixed thereto.

Illustrative of resin combination of layers are a combination of (a) apolypropylene or a polypropylene mixed with not more than 20% by weightof a polyethylene or an elastomer, and (b) a polyethylene or apolyethylene mixed with not more than 40% by weight of a polyethylene, acombination of a polystyrene and an ethylene-vinyl acetate copolymer,and a combination of an inorgamic filler containing polyolefin and apolyethyleneterephthalate.

Subsequently, as a preferable example able to be used for boiling orretort treatment, a multilayer structure composed of a combination of(A) a resin mixture layer of polypropylene base resin-polyethylene baseresin and (B) a high density polyethylene resin layer may be suitablyused. Illustrative of the polypropylene base resin to be used for theresin mixture layer are a random copolymer of propylene and an α-olefinsuch as ethylene, butene-1, pentene-1, 3-methylbutene-1, and4-methylpentene-1, and a mixture thereof, in addition to a highcrystalline propylene homopolymer. Herein, the random copolymer may alsobe a mixture thereof with a homopolypropylene obtained by multi-stagepolymerization. Within the above-mentioned copolymers, those preferredhave a ratio of the copolymerizing monomer of not more than 10 mol %.Further, in these polypropylene base resins, those having a melt index(MI) ranging from 0.1 to 20, preferably from 0.2 to 15, are suitable.

On the other hand, as the polyethylene base resins to be used for thesaid resin mixture layer, any of a low density polyethylene (a highpressure process low density polyethylene, a linear low densitypolyethylene, etc.), a medium density polyethylene, and a high densitypolyethylene may be used. Also, in addition to an ethylene homopolymer,a crystalline, low crystalline, or amorphous random or block copolymerof ethylene with an α-olefin, such as propylene, butene-1, pentene-1,3-methylbutene-1, and 4-methylpentene-1, or an unsaturated carboxylicacid such as vinyl acetate and acrylic acid, or a mixture thereof may beused. In the above-mentioned copolymers, those preferred have a ratio ofthe copolymerizing monomer of not more than 20 mol %. Further, in thesepolyethylene base resins, those having both of a melt index ranging from0.02 to 50, preferably from 0.05 to 30, and a density ranging from 0.850to 0.980 g/cm³, preferably from 0.900 to 0.975 g/cm³, are suitable.

The ratio between the above-mentioned polypropylene base resin andpolyethylene base resin is preferably selected among a range from 50:50to 97:3, more preferably from 60:40 to 95:5, by weight.

Further, at desire, the resin mixture may be blended with the thirdresin component in order to improve the compatibility or to control theadhesive property. Illustrative of the thrid resin component are, forexample, a modified polyolefin modified with an unsaturated carboxylicacid or a derivative thereof, an ethylene-vinyl acetate copolymer, anethylene-acrylate copolymer, an ethylene-propylene rubber, anethylene-propylene-diene rubber, a polybutene, a polyisobutylene, apolybutadiene rubber, a polyisoprene rubber, an atacticpoly-4-methylpentene-1, a styrene-butadiene rubber, anacrylonitrile-butadiene rubber, and an ion-crosslinked olefin copolymer(ionomer), and these may be used either individually or in combinationof two or more of them. Preferably, these third components are used in aquantity of not more than 30 parts by weight per 100 parts by weight ofthe polypropylene base resin.

Illustrative of the high density polyethylene resin to be suitably usedfor the other layer of the multilayer container, i.e. the high densitypolyethylene resin layer, are, in addition to an ethylene homopolymer,copolymers of ethylene and an α-olefin such as propylene, butene-1,pentene-1, 3-methylbutene-1, and 4-methylpentene-1, and the like. Inthese copolymers, those preferred have a ratio of the copolymerizingmonomer of not more than 10 mol %. In the high density polyethyleneresins, those having a melt index ranging from 0.01 to 50, preferablyfrom 0.02 to 20, and a density ranging from 0. 940 to 0.975 g/cm³ arepreferable, and they may be a mixture of those having differentdensities or molecular weights.

Though the multilayer container may be of two-layer type composed of theabove-mentioned resin layers, with the object of increasing the gasbarrier property or decreasing the deformation of the container, it maybe a multilayer type composed of three or more layers using layers ofother materials. Illustrative of the materials of other layers are, forexample, a resin layer, such as an ethylene-vinyl alcohol copolymer, apolyvinylidenechloride, nylon, and a polyethyleneterephthalate, or adeposited metal layer (e.g. depositted aluminium layer), which has agood gas barrier property. The layer composed of these other materialsmay be either one layer or a laminate composed of two or more layer, andmay also be provided with a resin layer containing from 10 to 80% byweight of an inorganic filler. In case of these multilayer structure,depending on the combination of the resins, lamination may be carriedout by using an adhesive resin such as a polyolefin modified with theabove-mentioned unsaturated carboxylic acid or the derivatives thereof,an ionomer, and the like.

The thicknesses of the said resin mixture layer and high densitypolyethylene resin layer are usually in the range from 10 to 1000 μm,preferably from 2 to 500 μm. The inner surface layer can be made thinsince the outer layers will maintain the strength of the multilayercontainer and all the inner surface layer has to do is protect thecontent and be heat sealed with a lid member.

The multilayer structure of the multilayer container is to be properlyselected depending on the sealant layer resin of the lid member, and,for example, when the sealant layer of the lid member is a polyethylenebase sealant layer, in case of the abovementioned combination of resinlayers, a high density polyethylene layer is to be used as the innersurface layer of the multilayer container. Herein, the multilayercontainer of the present invention may also has another layer such asseal layer on the inner side of the inner surface layer of themultilayer container at necessity, so long as it has the feature of thepresent invention that the multilayer container has a peeling layer.

When a metal layer such as iron (tin plate, galvanized sheet iron) andcopper is used as the outer layer of the present invention, for theinner surface layer, a resin layer having an easy peelability from themetal layer, for example, a polyolefin such as a polyethylene, apolypropylene, an ethylene-α-olefin copolymer, and an ethylene-vinylacetate copolymer; a mixture of the said polyolefin and a modifiedpolyolefin obtained by graft-modifying the above-mentioned polyolefinwith an unsaturated carboxylic acid such as maleic anhydride or aderivative thereof; an ionomer; and a polyethyleneterephthalate, isused. By the use of this multilayer container, an easily-openablepackaging container being tolerable to boiling and retort treatment andhaving an excellent strength, rigidity, pressure resistance, and heatstability can be produced. Further, the outer layer may be of paper,resin impregnated paper, or the like.

At the peripheral portion of the flange portion of the multilayercontainer, a notch 3 capable of cutting the inner surface layer atpeeling of the inner surface layer on the flange is formed. Any kind ofnotches will be available to this notch, so long as they can cut theinner surface layer at peeling of the lid member, and therefore, thenotch may as well extend into the layer contacting to the inner surfacelayer as extend only to midway of the inner surface layer. Further, theshape of the notch is not critical, and, for example, it may be U-shape,V-shape, cut line (half cut), etc. Also, it may be cut in from theunderside of the inner surface layer. Further, the notch may be formedcompletely circularly at all of the inner peripheral portion of theflange portion, but a part of the inner peripheral portion may as wellbe left unnotched. In case of peeling the lid member with a part of itnot peeled, the part alone is to be unnotched.

Referring to FIG. 2 which is a sectional view illustrating a state wherethe multilayer container of the present invention is covered with a lidmember 5 and heat sealed, a reference numeral 6 represents a heat sealportion, and the multilayer container and the lid member arepeeling-resistively heat sealed at the flange portion of the multilayercontainer. The peeling strength of the seal portion sealing the innerlayer of the multilayer container with the lid member is larger than theinterlaminer strength of the inner layer of the multilayer container,and the preferable peeling strength is usually not less than 2.0 kg/15mm, more preferably not less than 2. 5 kg/15 mm (tensile speed: 300mm/min). A reference numeral 7 represents a picking portion for makingthe peeling easy. As the sealing method, conventional methods forheating sealing plastic films such as heat seal method, impulse sealmethod, high-frequency bonding method, and ultrasonic wave bondingmethod may be used.

Although the lid member 5 is one-layer film in the multilayer containershown in FIG. 2, it would not be restricted, and it may be one-layerfilm or a multilayer film depending on its embodimented style. When thelid member is formed of a multilayer film, the multilayer films to besuitably used are those composed of a substrate and a sealant layer,wherein the substrate is made of a one-layer film of a plastic, amultilayer film of plastics, a paper, an aluminium foil, a complex layerthereof, or the like, and the sealant layer is composed of a resinhaving an easily-heat sealing property at the inner surface layer of themultilayer container such as those made of a polyethylene, apolypropylene, an ethylene-α-olefine copolymer, or an ethylene-vinylacetate copolymer.

Referring to FIG. 3 which is a sectional view showing a multilayercontainer of another embodiment according to the present invention, arib 8 is formed at the outer periphery of the flange portion. A curlalso may be formed instead of the rib. In these cases, though thepeeling of the lid member might be hard, a second notch formed at theouter periphery of the flange portion will make it easy.

The multilayer container of the present invention can be produced byproducing a flanged multilayer container which can be delaminatedbetween the inner surface layer and the layer contacting to the innersurface layer, and then, by the means of pressing with a notching blade,pressing with a heating blade, cutting with a cutting edge, a heatingmeans, or a combination thereof, forming a notch capable of causing acutting of the inner surface layer at the inner peripheral portion ofthe flange portion at delamination of the inner surface layer of theflange portion.

The multilayer container can be produced from the resins of theabove-mentioned combination by the way of thermo-forming, such as vacuumforming and pressure forming, of a co-extrusion multilayer sheet or alaminate sheet, multilayer injection molding, multilayer injection blowmolding, multilayer blow molding, or the like. Further it may also beproduced by draw forming a multilayer sheet composed of a metal, such asaluminium, and a resin or thermoforming a multilayer film on the insideof a paper container.

As the laminating processing, for example, extrusion lamination,hot-melt lamination, dry lamination, wet lamination, and the like may beemployed.

The preferable means for forming a notch is processing with a heatingblade or the like, and illustrative of the heating means, which is notcritical, are electric-heater means, heating with a heating medium,impulse heating, high frequency heating, ultrasonic wave heating, andthe like. These means are combined with a U-shaped or V-shaped ringpressing member to form a notch. When pressure and heat are employedjointly, it is preferable that the inner surface layer of the multilayercontainer is made of a resin having a melting point or a softening pointlower than those of the outer layer and, at the same time, thickness ofthe inner surface layer is not more than 200 μm. Particularly, by usinga heat unfusible material such as a metal for the outer layer, the notchcan be certainly formed only in the inner layer.

Referring to FIG. 4a, FIG. 4b, FIG. 4c, FIG. 4d, and FIG. 4eillustrating the method for forming a notch, FIG. 4a shows the statewhere a notch is being formed by pressing a notching blade, FIG. 4bshows the state where a notch is being formed by recessing with acutting blade, FIG. 4c shows the state where a notch is being formed byprojecting a multilayer sheet from underside and then cutting theprojecting part, FIG. 4d shows the state where a notch is being formedby pressing a heating ring, and FIG. 4e shows the state where a notch isbeing formed by ultrasonic wave heating.

Formation of a notch by the above-mentioned methods may be carried outat thermo-forming of a container, at punching of the container, or afterpunching of the container.

The present invention further provides a method for producing amultilayer container capable of easily producing a multilayer containerfor easily-openable packaging containers which has a notch formed into aflange portion dimensionally accurately in position, depth, or the like,and, capable of incorporating a component for forming a notch to aconventional machinary.

The method for producing the multilayer container with a notch of thepresent invention will be explained referring to the appended drawings.FIG. 5 illustrates an example of the process for producing a multilayercontainer by the method of the present invention, and FIG. 6 is apartially sectional illustration of an example of the thermo-formingsection in FIG. 5.

In FIG. 5, a reference numeral 31 represents a multilayer sheet composedof thermoplastic resins, and the multilayer sheet is thermo-formed intoa flanged multilayer container provided with a notch at the flangeportion, by feeding it to a heating step 32 to heat to a temperature atwhich the sheet can be thermo-formed, then feeding it to athermo-forming step 33.

In the above-mentioned thermo-forming step, as shown in FIG. 6, themultilayer sheet 31 heated to a temperature at which it can bethermo-formed is usually thermo-formed into a container by holding themultilayer sheet with a sheet press ring 113, then fitting it to a mold111 by a differential pressure means such as vacuum forming, pressureforming, and the like. At this time, the notching processing isconducted with a ring notching blade 114 before, after, orsimultaneously with punching of the periphery of the container's flangeportion with a punching blade 112. A reference numeral 115 represents avent of the mold 111, and a reference numeral 116 represents an airpressing channel provided in the sheet press ring 113.

Also, the punching blade 112, sheet press ring 113, and ring notchingblade 114 may be operated simultaneously or sequentially. Further, thetime at which a notch is to be formed is not critical, so the notch maybe formed before forming of the container (at the time when the sheet isholded), after heat treatment following to forming of the container(particularly effective for PET and the like), or at punching of thecontainer. The punching of the multilayer container is not necessarilycarried out in the forming process, and it may also be carried out inthe next process, because the present invention is characterized inthat, in case of a circular container, a notch is formed at anequivalent distance from the center. Furthermore, though the temperatureof the ring notching blade 114 may be any of a room temperature, a lowtemperature, and a high temperature, it is properly selected accordingto the kind of resins, the time of forming notch, the depth of the notchto be formed, or the like.

Illustrative of the sequence of operating the punching blade 112, thesheet press ring 113, and the ring notching blade 114 are, for example,(A) ○1 thermo-forming, ○2 descent of the sheet press ring, ○3 descent ofthe ring notching blade, ○4 descent of the punching blade, (B) ○1descent of the sheet press ring, ○2 descent of the ring notching blade,○3 thermo-forming, ○4 descent of the punching blade, and (C) ○1 descentof the sheet press ring and the ring notching blade, ○2 thermo-forming,○3 descent of the punching blade.

The present invention also provides an apparatus for forming a notchcapable of forming a notch dimensionally accurately at the flangeportion of a multilayer container.

Referring to the appended drawings in order to illustrate examples ofapparatuses for forming a ring notch of the present invention, FIG. 7and FIG. 8 are sectional rough explanatory drawings of apparatuses forforming a ring notch of different embodiments of the present invention;FIG. 7 shows an apparatus wherein a ring blade is situated in the upperpart and a container guide is not installed inside the ring blade, andFIG. 8 shows an apparatus wherein a ring blade is situated in the lowerpart and a container guide is installed inside the ring blade.

In those drawings, a ring blade 43 is a means for forming a ring notchon the upper surface of the flange portion of a multilayer container andis equipped with a heater 45 as heating means. The ring blade has acontrollable blade length, and referring to the edge shape, those havingthe edge shapes shown in FIGS. 9(A), (B), (C), (D), (E), (F), and (G),or the like may be used.

When a ring blade having an edge of the shape shown in FIG. 9(G) isused, it is preferable to use a multilayer container in which themelting point or the softening point of the resin of the notch forminglayer is lower than that of the resin of the next layer. The state of anotch to be formed in this case is shown in FIG. 10.

As shown in FIG. 7, although a sufficient accuracy can be obtained innotch forming without a container guide inside a ring blade, as shown inFIG. 8, it is preferable to install a container guide 46 inside the ringblade 43 in order to increase the forming accuracy furthermore. Thoughthe shape of the ring blade 43 varies depending on the shape of theflange portion of the multilayer container, usually, it has a continuousring shape such as circular shape, triangular shape, square shape, andoval shape, and as the material thereof, for example, high carbon steel(Tomson blade), chrome-stainless steel, aluminium, ceramics, or the likemay be employed.

On the other hand, a supporting member 47 serves for supporting a flangeportion at forming of a notch and has a container receiving portion 44.The supporting member 47 and the above-mentioned ring blade 43, at leastone of them is capable of ascent and descent, are each secured to anapparatus proper 41 and 41' through an elastic member 42 and 42'. As theelastic member 42, 42', for example, a spring or a dashpot may be used.By the use of the elastic member, a uniformity of pressing pressure andan increase of the accuracy of the notch forming depth can be obtained.Also, when a container guide 46 is provided inside the ring blade 43, itis preferable to secure the container guide to a ring blade mountingmember through the elastic member 42.

The multilayer containers to be provided with a notch at the flangeportion may be individuals or multiple containers formed in one sheet.

In case of forming notches to a plurality of containers in the sameinstance, it is advantageous to make the notching tool minutely movableby the aid of the container receiving portion or the container guide or,as shown in FIG. 11, provide a score 49 so that a plurality ofcontainers 48 formed in one sheet can each move minutely.

In order to form a notch at the flange portion of the multilayercontainer by using the apparatus of the present invention, at first, themultilayer container is placed into the container receiving portion ormounted onto the container guide 46, then, in the former case, byelevating the supporting member 47 or lowering the ring blade 43, or byboth of them, a notch is formed at the flange portion of the container.In the latter case, a notch is formed at the flange portion of thecontainer by elevating the ring blade 43 or lowering the supportingmember 47, or by both of them. At this time, the temperature of the ringblade 43 is properly controlled depending on the kind of resin, the timeof forming of a notch, the depth of the notch to be formed, and thelike.

The present invention further provides an easily-openable packagingcontainer having a high seal strength and a good easy openability,wherein a multilayer container is filled with an article and heat sealedwith a lid member.

The easily-openable packaging container of the present invention will beexplained according to the drawings. FIG. 12 is a partially sectionalview of an easily-openable packaging container of an embodimentaccording to the present invention wherein the above-mentionedmultilayer container and lid member are employed.

A reference letter A represents a multilayer sheet usually formed of aco-extrusion sheet or the like which is formed into a multilayercontainer 10 by vacuum forming or pressure forming. The multilayercontainer is provided with a flange portion 4 for heat sealing a lidmember.

The multilayer structure A of the multilayer container is composed of aninner surface layer 1 which can be peeling-resistively heat sealed to asealant 12 of the lid member and an outer layer 2 whose adhesivestrength to the inner surface layer is smaller than that of thepeeling-resistive heat seal.

The inner surface layer of the multilayer container and the lid memberare heat sealed at a heat seal portion 6 in the flange portion of thecontainer.

At the opening portion side of the inner surface layer of the multilayercontainer on the flange portion, a ring notch 3 is cut in.

FIG. 13 is a partially sectional view of an easily-openable packagingcontainer of another embodiment according to the present invention. Inthis case, the periphery of the flange portion of the container iscurled toward inside. In this case, a notch 14 shown in the figureformed into the inner surface layer at the peripheral side of the flangeportion of the container permits the inner surface layer to be peeledeasily.

The periphery of the lid member is projected to the outer side of themultilayer container to form a picking portion 7, to serve theconvenience of picking at opening.

The easily-openable packaging container in which the multilayercontainer of the present invention is filled with an article and heatsealed with a lid member can be easily opened by the following simplemotion.

For example, referring to FIG. 12, the picking portion 7 is liftedupward. Thereupon, delamination of the multilayer container occursbetween the inner surface layer 1 and the layer 2 contacting thereto,and the inner surface layer is peeled to as far as a notch 3 causing thelid member to be peeled. Therefore, the opening can be easily performedeven if the lid member and the multilayer container arepeeling-resistively heat sealed.

Also, as against the conventional method in which the peeling occurs ata seal area, a stable opening strength can be obtained because of theabsence of notch effect caused by an imperfect seal at seal end,difference in sealing condition, influence of foreign matters, and thelike. Further, since peeling can be performed easily even if the peelingstrength of heat seal is increased, the easily-openable packagingcontainer will be of a so good heat-resistance as to resist to boilingand retort treatment.

Referring to FIG. 13, by lifting the picking portion, the inner surfacelayer and the outer layer is delaminated from a notch on the outerperipheral portion, and thereafter the lid member can be easily openedas mentioned above.

In the easily-openable packaging container of the present invention, itis preferable to leave a space between the inner end of the heat sealportion and the notch. The length of the space t is from 0.5 to 10 mm,preferably 1.5 to 5 mm. The space makes a packaging container having apeeling strength of from inside of a container larger than that of fromoutside, so that a packaging container being excellent in packaging offoodstuffs where a heat resistance and pressure resistance is requiredagainst boiling, retort treatment, and the like can be obtained. Thoughthe reason is not apparent, it is supposed that, in case of peeling frominside, the stress concentrates to point X and the shearing strength ofthe Y-Z area becomes the peeling strength of from the point Y so thatthe peeling strength is increased. If the length of t is less than 0.5mm, the peeling strength of from inside of the container isn'tsufficiently larger than that of from outside, and, a length more than10 mm is not practical.

When a space t is provided as mentioned above, an accurate control ofthe heat seal position on a plane flange portion becomes difficult.Thus, in case of the easily-openable packaging container, it ispreferable to provide a ring notch at a non-heat seal surface more innerthan the heat seal portion.

FIG. 14 is a partially sectional view of an easily-openable packagingcontainer of an embodiment according to the present invention. In thiscase, the flange portion 4 of the multilayer container is not completelyplane, the inner peripheral portion of the flange portion inclinesgradually toward the inner side of the multilayer container, and a notch3 is provided on the inclined surface. That is to say, the notch isprovided on a non-heat seal surface 15, i.e. the inclined surface of theflange portion. Now, representing the space from the point where thenon-heat seal surface of the flange portion begins to the notch by t',heat sealing by the use of such multilayer container prevents heatsealing in the space (length t') from the outer end of the non-heat sealsurface to the notch, and controls the length of t to at least thelength of t' even if the heat seal portion deviates, so that asufficient pressure resistative sealing property and an easy openabilitycan be exhibited.

FIG. 15 is a partially sectional view of an easily-openable packagingcontainer of another embodiment according to the present invention. Inthis embodiment, in order to provide a notch at a non-heat seal portion,a difference in level is provided in the inner peripheral portion of aflange portion 4, and a notch 3 is provided at a dropped surface 16 ofnon-heat seal surface.

FIG. 16 is a partially sectional view of an easily-openable packagingcontainer of an embodiment according to the present invention in which arib 17 for enforcement is formed at the outer peripheral portion of aflange portion 4. This container is provided with a notch 14 in theinner surface layer 1 at the outer peripheral portion of the flangeportion.

In addition to such a inclined surface as shown in FIG. 14 or a droppedsurface as shown in FIG. 15, any non-heat seal surface will be employed,so long as it consists an area unable to contact to a lid member at heatsealing, such as, a curved surface and the like. Since a notch isprovided at a non-heat seal surface, by using a relatively wide heatseal ring at the time when a lid member and a multilayer container isheat sealed, all of the flat surface portion of the flange portion canbe sealed even if the seal shifts, so that both of a uniform length of tand a uniform position of the outer end of the heat seal portion can beobtained. Therefore, the heat seal operation can be easily conducted,and a stable opening strength can be obtained.

Further, in the easily-openable packaging container of the presentinvention, it is preferable to make a heat unfusible layer on at leastone of flange portion inside the heat seal portion and the lid member,and to provide a ring notch inside the heat seal portion.

FIG. 17a is a partially sectional view of an easily-openable packagingcontainer of another embodiment according to the present invention. Inthis case, a heat unfusible layer 18 is formed inside a heat sealportion 6 of a flange portion 4 of a multilayer container, and thisportion will not be sealed when a lid member is heat sealed to theflange portion with a heat seal ring. Therfore, a fixed space can beprovided between the inner end of the flange portion and the notch.Though the heat unfusible layer is provided at flange portion in FIG.17a, the heat unfusible layer may also be provided on a lid member. Thematerial of the heat unfusible layer is not critical so long as it canprevent the heat fusion of a flange portion and a lid member at the timewhen the flange portion and the lid member is heat sealed. A notch 3 isprovided at the heat unfusible portion of the inner surface layer in theflange portion previously. Heat sealing by using such a container makesit possible to control the length of t to be fixed, and thus asufficient sealing property and an excellent easy openability can beexhibited.

FIG. 17b is a partially sectional view illustrating a state where thelid member shown in FIG. 17a is being peeled. Following to theoccurrence of a delamination of a multilayer container, the innersurface layer is cut at the notch resulting in the peeling at the lidmember.

FIG. 18a and FIG. 18b are sectionally explanatory drawings illustratinga method for conducting both heat sealing of the easily-openablecontainer of the present invention and forming of a notchsimultaneously. A heat seal ring 19 is provided with a sealing member 20for heat sealing and, at a distance t from the seal portion, a ringmember 21 in one body. By conducting heat sealing and forming of a notchsimultaneously like this, a fixed t and a good operation efficiency canbe obtained and, further, heat sealing and forming of notch can beperformed without damaging the shape of the container. In this example,however, it is required that the condition of the length of the ringmember or the like is so predetermined as to cause no damage of the lidmember at forming of a notch. Further, in order to keep the shape of themultilayer container from damage, it is preferable to employ anunfusible material, such as a resin having a melting point higher thanthat of the material of the inner surface layer 1, a metal, or the like,as the material of the layer 2 contacting to the inner surface layer.Such a heat unfusible layer provided thereto permits a notch to beformed at the same time or after heat sealing, and, therefore, theconventional packaging process may be employed.

Further, when a rib or a curl is provided to the easily-openablepackaging container of the present invention in order to improve thestrength of the flange portion of the multilayer container, the handlingfeeling, and the design quality, it is preferable to provide a cut-offportion in the vicinity of the flange portion of the rib portion or thecurl portion.

FIG. 19 is a perspective view of an easily-openable packaging containerof an embodiment according to the present invention in which a cut-offportion 22 is porvided at a rib portion 8. In this case, a cut-offportion 22 extending from the underside to the flange level is providedin the rib portion which is provided to the end of the flange portion ofa multilayer container. The inner end portion of the flange portion 4 isformed into a non-heat seal surface 15 of a gradually inclined plane,and a notch 3 is provided to the non-heat seal surface 15.

In the easily-openable packaging container of the present invention, thecut-off portion, which is provided to the rib portion or curl portionnear the flange level, exposes a cross section of the inner surfacelayer of the multilayer container and the layer contacting thereto nearthe flange level, and gives occasion for peeling of the inner surfacelayer of the multilayer container at opening. Though, in FIG. 19, thecut-off portion extends from the lowest portion of the rib portion toflange level, the size and shape is not critical so long as it canachieve the above-mentioned purpose. Therefore, the cut-off portion maybe a score, a hole, or the like provided in the rib or curl portion nearflange level. However, it is necessary to locate it near flange level,and, if it is located too far from the flange level, the occasion forpeeling of the inner surface layer of the multilayer container can notbe obtained.

Further, in the present invention, since the peeling of the innersurface layer starts from the cut-off portion, it is enough to provide anotch only to the inner end portion of the flange portion. That is, anotch in the outer peripheral portion of the flange portion is notalways required since the edge effect caused by heat seal enablescutting.

FIG. 20 is a perspective view of a multilayer container to be used foran easily-openable packaging container of another embodiment accordingto the present invention. In this case, a cut-off portion of a ribportion 8 is not cut at a position where it contacts to a flange portion4, but arises to the flange level to form a flat surface 23. Also, inthis case, either side of the flat surface 23 may be connected to therib 8.

FIG. 21 is a partially sectional view of a cut-off portion of aneasily-openable packaging container of the present invention in whichthe multilayer container shown in FIG. 19 is heat sealed with a lidmember. A notch 3 is provided to a non-heat seal surface 15 of a flangeportion 4. A heat seal portion 6 extends to the outer periphery of theflange portion 4. A lid member (12, 13) is provided with a pickingportion 7 for making opening easy. FIG. 22 is a partially sectional viewof a part including a cut-off portion of an easily-openable packagingcontainer of the present invention in which a lid member is heat sealedto the multilayer container shown in FIG. 20. In both of FIG. 21 andFIG. 22, a cross section of the inner surface layer 1 of the multilayercontainer and the layer contacting thereto is exposed by the cut-offportion, near the flange level of the multilayer container. Thus, whenthe picking portion 7 is holded up to open, delamination begins betweenthe inner surface layer 1 and the layer 2 contacting thereto exposed bycutting off, then the inner surface layer in the outer periphery of theheat seal portion is cut along the outer end of the heat seal portionsubsequently, and the inner surface layer is further peeled causing theprogress of opening. Also, in the easily-openable packaging container ofthe present invention, in order to further increase the openability,instead of providing a picking portion to a lid member as mentionedabove, a tongue peace may be substituted for the picking portion byplacing it on the flange portion over the cut-off portion and heatsealing a lid member. Further, instead of inserting a tongue piece, apicking portion may be provided only at a part of the lid member overthe cut-off portion to serve as a tongue piece portion having a tongueshape.

When this packaging container having a rib portion or a curl portion isopened, for example, in FIG. 22, the picking portion 7 is raised upwardfor a start. Thereupon, delamination begins between the inner surfacelayer 1 and the layer 2 contacting thereto exposed by cutting off, thenthe inner surface layer in the outer periphery of the heat seal portionis cut, thereafter, delamination progresses between the inner surfacelayer 1 and the layer 2 contacting thereto, and the inner surface layeris peeled to the notch 3, resulting in the peeling of the lid member.Thus, opening can be easily achieved even if the lid member and themultilayer container is heat sealed peeling resistively. Further, whenanother notch is further provided also to the outside of the heat sealportion of the flange portion, cutting and peeling of the inner surfacelayer becomes more easy, and the openability increases.

Also, when, as shown in FIG. 23, the easily-openable packaging containerof the present invention is provided with notches not only to the innersurface layer at the container's opening portion side of the flangeportion but also to the outer layer at the peripheral portion of thecontainer, the outer layer separates into two at the notch 24 as shownin FIG. 24, then delamination occurs between the inner surface layer 1and outer layer 2 of the container, thus it can be opened easily.

As mentioned above, in comparison with the conventional methods in whichopening is performed by peeling a lid member and a multilayer containerfrom a sealing area, since the easily-openable packaging container ofthe present invention is opened by delaminating the multilayercontainer, it can be opened easily even if the lid member and themultilayer container is peeling resistively heat sealed. Because of theabove-mentioned posibility of strong sealing, the range for sellectingthe material and shape of the lid member is so wide that, for example, adrop lid as shown in FIG. 25 also may be used. Packaging using a droplid has such advantage that the residual air in the container can bereduced causing an increase of the keeping quality of foodstuffs.However, opening of containers made by conventional packaging methodshas been difficult, because, when a content such as soup is filled inthe container, the content overflowed by setting of a drop lid causes sobad effects to the seal portion at heat sealing that a strong sealing isrequired. However, since the packaging containers of the presentinvention can be sealed strongly, a drop lid can be suitably used forthem. The shape of the drop lid is not critical so long as it can beengaged with the opening portion of the multilayer container to expelair, and it may have a curved shape, a shape having a flat bottom face,or the like.

In the method for filling and packaging an article of the presentinvention, a notch is provided to an inner surface layer of a flangeportion before or after filling of an article. The notch may be formedby, for example, a physical method using a notching blade or a cuttingblade, a heating method by heat-ray fusing cutting (impulse) or a heatblade, a mechanical vibration method using ultrasonic wave, aninternally exothermic method using high frequency, or the like. Whensuch a notch is provided before filling of an article, an article issubsequently filled in the said container, then a lid member is heatsealed to the flange portion. For example, a notch can be easily formedby pressing a ring notching blade having a V-shaped edge (heated atneed). In this case, a notch forming ring may be installed to aconventional non-heating hitting ring for preheating a lid member bynon-heating hitting before sealing. In case of a container with a tonguepiece for peeling, it is preferable to heat seal the end portion of thetongue piece securely to lid member. Also, it is desirable to form apenetrating notch in the sheet. When a notch is formed after filling ofan article, a lid member is subsequently heat sealed to the flangeportion.

After a lid member is heat sealed in this manner, the periphery of theheat seal portion is punched to obtain a package having a peelableopening part. In this case, two or three containers may be punched inone body.

In the above-mentioned method for filling and packaging of the presentinvention, "forming of a container" means not only forming in a throughline but also a multilayer container formed previously.

The apparatus for filling and packaging an article of the presentinvention is an apparatus for a through line method within theabove-mentioned method for filling and packaging. Referring to FIG. 26which is an explanatory drawing showing an example of the said apparatusincorporating a container forming means, a multilayer sheet 51 is heatedby a heating means 52, then fed to a container forming means 53. In thecontainer forming means, the multilayer sheet 51 is formed into acontainer by, for example, vacuum forming or pressure forming.

Then, the container thus formed is fed to an article filling means 54 tobe filled with an article, thereafter, in a notch forming means 55, anotch is provided to an inner surface layer of a flange portion inside aheat seal portion of the flange portion and a lid member. In theapparatus of the present invention, the above-mentioned article fillingmeans and the notch forming means may be inverted, and the notch formingmeans may include a non-heating hitting means. Subsequently, a lidmember is heat sealed to the flange portion of the container in a lidmember heat sealing means 56, then the periphery of the heat sealedportion is punched to obtain a package having a peelable opening part. Areference numeral 58 represents a lid member film.

According to the method and apparatus of the present invention, aneasily-openable packaging container can be produced by using amultilayer sheet as a starting material without addition of specialprocesses, and, in a certain case, by a through process comprising fromforming of a container to punching. Therefore, the content is neverpolluted, and the packaging cost is low.

EXAMPLES

The present invention will be described in more details referring to thefollowing examples, but the present invention is not to be limited tothese examples.

EXAMPLE 1

A multilayer sheet [I] mentioned below was formed by co-extrusionprocess.

inner layer: a high density polyethylene 70 μm [IDEMITSU POLYETHYLENE440M produced by Idemitsu Petrochemical Co., Ltd., density: 0.96 g/cm³,MI: 0.9 g/10 min., molecular weight distribution: narrow]

outer layer: a polypropylene base resin layer 200 μm: a mixture of 80%by weight of a polypropylene [IDEMITSU POLYPRO E-100G produced byIdemitsu Petrochemical Co., Ltd., MI: 0.6 g/10 min.], 15% by weight of alow density polyethylene [PETOROSEN 172 produced by Toyo Soda Mfg. Co.,Ltd., density: 0.92 g/cm³, MI: 0.3 g/10 min.], and 5% by weight of ahigh density polyethylene [IDEMITSU POLYETHYLENE 530B produced byIdemitsu Petrochemical Co., Ltd.]

By using the multilayer sheet [I], a flanged multilayer container of 60mm φ×40 mm (height) was formed by pressure thermo-forming. A notch wasformed at the inner peripheral portion of the flange portion of thismultilayer container by the following three methods.

(1) A notch was formed by pressing a ring notch blade of 0.8 mm inthickness having a sharp edge.

(2) A notch was formed by pressing a seal ring of 1 mm in width at from170° to 190° C. and 2 kgf/cm² for one second.

(3) A notch is formed by contacting a ring notching blade to a part tobe provided with a notch, and treating with ultrasonic wave from theopposite surface (900W, radiating time: 0.05-0.09 sec.).

The inner layers of multilayer containers produced by these methods werepeeled, and then all of the inner layers were cut at the notch portion.

When a lid member (1) made of an orientednylon/polyvinylidenechloride/linear polyethylene (15μ/20μ/40μ) was heatsealed to the multilayer container at the flange portion and the lidmember was peeled, delamination of the multilayer sheet of themultilayer container occurred, then the inner layer of the multilayercontainer was cut at the notch portion, and opening was performedeasily.

EXAMPLE 2

A multilayer sheet [II] (0.8 mm in thickness) consisting of six layersof four kinds was formed by co-extrusion forming.

    a:b:c:d:c:b=50:350:20:30:20:350(μm)

a: a high density polyethylene [IDEMITSU POLYETHYLENE 440M produced byIdemitsu Petrochemical Co., Ltd., density: 0.96 g/cm³, MI: 0.9 g/10min., molecular weight distribution: narrow]

b: a mixture of 80% by weight of a polypropylene [IDEMITSU POLYPROE-100G produced by Idemitsu Petrochemical Co., Ltd., MI: 0.6 g/10 min.]and 20% by weight of a low density polyethylene [PETOROSEN 172 producedby Toyo Soda Mfg. Co., Ltd., density: 0.92 g/cm³, MI: 0.3 g/10 min.]

c: a polypropylene modified with maleic anhydride [IDEMITSU POLYTAC E100produced by Idemitsu Petrochemical Co., Ltd.]

d: a saponificated ethylene-vinyl acetate copolymer [EVAL EP-F101produced by Kuraray Co., Ltd., ethylene content: 32 mol%, MI: 1.3 g/10min.]

A flanged container of 60 mm φ×40 mm (height) was produced by heatingthe multilayer sheet [II] to formable temperature, inserting it on amold as shown in FIG. 6, lowering a sheet press ring, forming bypressure thermo-forming, lowering a ring notching blade, elevating aring notching blade, and lowering a punching blade. A ring notch of 60μm in depth was formed in the flange portion as shown in FIG. 27.

Thereafter, a lid member (1) [e:f:g] used in Example 1 was heat sealedto the flange portion under conditions of temperature of 170° C.,pressure of 4 kg, 1.5 seconds, and double pressing sealing, using thelinear low density polyethylene layer as sealing layer.

Peeling test for the flange portion of the sealed container wasconducted in accordance with JIS K 6854. Further, after the containerwas filled with water and applied to a retort treatment of 120° C., 30minutes, peeling test was conducted again. The results are shown inTable. Herein, there was no breakage after the retort treatment, and thecontainer had an excellent gass barrier property.

EXAMPLE 3

A container was produced by the same procedure in Example 2 providingthe high density polyethylene was altered to IDEMITSU POLYETHYLENE 530B[Idemitsu Petrochemical Co., Ltd., MI: 0.3 g/10 min., density: 0. 957g/cm³, molecular weight distribution: broad]. The results are shown inTable.

                  TABLE                                                           ______________________________________                                        Peeling strength                                                                               Example 2 Example 3                                                           (g/15 mm) (g/15 mm)                                          ______________________________________                                        opening side                                                                              before retort                                                                            950         700                                                    treatment                                                                     after retort                                                                             700         550                                                    treatment                                                         non-opening side                                                                          before retort                                                                            3,500       2,900                                                  treatment                                                                     after retort                                                                             3,100       2,500                                                  treatment                                                         ______________________________________                                    

EXAMPLE 4

A multilayer container having a flange portion of 50 mm φ in openingportion, 40 mm φ in bottom face, 20 mm in height, and about 200μ inthickness was formed from an aluminium sheet coated with a polypropylenemodified with maleic anhydride (0.6 mm in thickness, resin layer 150μ)by stretch forming. At the inner resin layer of the multilayer containerin the inner portion of the flange portion, a ring notch extending tothe metal layer was formed with a heat blade along the inner peripheryof the flange portion. Then, to this container, a lid member which hadan aluminium foil layer of 20μ in thickness and a sealing layer of 50μin thickness formed from a polyethylene containing ethylenevinyl acetatecopolymer modified with maleic anhydride was heat sealed. The space tbetween the inner end of the heat seal portion and the notch wasadjusted to 1 mm.

When the sealed lid member was peeled, delamination occurred between themetal layer and the easily-peelable resin layer, and opening wasperformed easily with a uniform peeling force.

EXAMPLE 5

A multilayer container of 60 mm in diameter of opening portion, 50 mm indiameter of bottom face, and 25 mm in height was produced from amultilayer sheet by pressure thermo-forming. The inner layer of theflange portion was a high density polyethylene (50μ), and the outerlayer was a polypropylene blended with 10% by weight of anethylene-propylene rubber (500μ).

At the flange portion of the container, a ring notch extending nearly tothe outer layer was formed.

Then, a lid member of a multilayer film (PET/EVOH/LLDPE: 12μ/20μ/30μ)was heat sealed by using LLDPE as the sealing layer, to obtain aneasily-openable packaging container. When the container was peeled froma picking portion, delamination of the multilayer container occurred,and peeling feeled good.

EXAMPLE 6

A multilayer sheet and a lid member having the layer structure shown inFIG. 28 were produced.

On an co-extruded multilayer sheet [II] consisting of

a: a mixture of 80 parts by weight of a polypropylene [IDEMITSU POLYPROE-100G produced by Idemitsu Petrochemical Co., Ltd., density: 0.91g/cm³, MI: 0.6 g/10 min.] and 20 parts by weight of a low densitypolyethylene [PETOROSEN 172 produced by Toyo Soda Mfg. Co., Ltd.,density: 0.92 g/cm³, MI: 0.3 g/10 min.]

b: a high density polyethylene [IDEMITSU POLYETHYLENE 440M, density:0.96 g/cm³, MI: 0.9 g/10 min.] (layer a: 200 μm in thickness, layer b:50 μm in thickness),

a notch of 70 μm in depth was formed.

To this sheet, the lid member (1) [e:d:c] used in Example 1 was heatsealed under the conditions of temperature of 170° C., pressure of 1.5kg/cm², and 1.5 seconds, using the linear low density polyethylene layeras the sealing layer, altering the space t. 180° peeling strength of theseal portion was measured in accordance with JIS K 6854. The result wassuch that delamination occurred between a and b, and the peelingstrength was as follows;

    ______________________________________                                        t = 0 mm               0.54   kg/15 mm                                        1 mm                   2.2    kg/15 mm                                        3 mm                   3.5    kg/15 mm                                        5 mm                   >4     kg/15 mm                                        ______________________________________                                    

Next, containers each having t of 2 mm and 4 mm, above-mentioned layerstructure, and shape shown in FIG. 12 were produced. Then, after waterwas filled, these containers were heat sealed and retort treated at 120°C. for 30 minutes. These containers were not opened at all.

Each containers had an opening strength of about 0.9 kg/15 mm beforeretort treatment, and about 0.6 kg/15 mm after retort treatment, and waseasily opened. The peeled surfaces were smooth.

Further, an internal pressure was applied with a pump to a sealedcontainer having t of 2 mm produced by heat sealing a lid member to acontainer filled with water, and the internal pressure at which the lidmember was peeled was measured. (average value of five containers)

before retort treatment 1.45 kg/cm²

after retort treatment 1.30 kg/cm²

(conditions of retort treatment: 120° C., 30 minutes)

When the internal pressure is applied, after the lid member expanded toa hemispherical shape from the inner end of the sealing area (point X),delamination of the multilayer container occurred.

EXAMPLE 7

A multilayer container having a flange portion of 60 mm φ×40 mm (height)was formed from the multilayer sheet [I] of Example 1 by vacuum andpressure thermo-forming.

In the flange portion of the multilayer container (8 mm in width), theinner portion (3 mm in width) was formed into a non-heat seal surface ofa gradually inclined plane. A ring notch was formed at 2 mm distancefrom the outer end of the non-heat seal surface by pressing a ringhaving a V-shaped edge heated to 160° C.

When the inner surface layer of the flange portion of the multilayercontainer having a notch obtained by the above-mentioned method waspeeled, the inner surface layer was cut at the notch portion.

When the lid member (1) used in Example 1 was heat sealed to themultilayer container at the flange portion, the non-heat seal surfacewas not heat sealed. Further, when the lid member was peeled,delamination of the multilayer container occurred, then the innersurface layer of the multilayer container was cut at the notch, so thatopening was easily conducted. The opening force was stable.

EXAMPLE 8

A flanged multilayer container of 60 mm φ×40 mm (height) was formed fromthe multilayer sheet [I] used in Example 1 by vaccuum and pressurethermo-forming. A heat unfusible layer of a silicone resin as shown inFIG. 17a was provided to the inner portion of the flange portion of themultilayer container. The multilayer container was covered with the lidmember (1) used in Example 1, then, by the use of a heat seal ring (t=3mm, width of the extruding ring: 1 mm), heat sealing and forming of anotch were conducted simultaneously, at a temperature of 170° to 190°C., and pressure of 2 kgf/cm², for one second, as shown in FIG. 18b.

When the container thus formed was peeled the lid member, delaminationof the multilayer sheet of the multilayer container occurred, then theinner surface layer of the multilayer container was cut at the notch sothat the container was opened easily. Also, the opening force wasstable.

EXAMPLE 9

A flanged multilayer container of 60 mm φ×40 mm (height) having a ribportion of 6 mm in length was formed from the multilayer sheet [I] usedin Example 1 by vaccuum and pressure thermo-forming. At the innerperipheral portion of the multilayer container, an inclined plane ofθ=20° in angle of inclination was provided, and a notch of 60 μm indepth was formed at a position of t=2 mm. At the rib portion, twoincisions of 7 mm in length each extending from the lower end of the ribto the flange level were made with the space of 10 mm, then, after thecut piece between the incisions were lifted to make a flat surface, theflat surface was cut away. To the multilayer container, a lid memberhaving a tongue portion and the same layer structure of the lid member(1) used in Example 1 was so heat sealed that the tongue portion wouldlocated on the cut-off portion of the multilayer container.

When thus obtained easily-openable packaging container was opened bylifting the tongue piece of the lid member, delamination began from thecut-off portion under the tongue piece, then the inner surface layer wascut at the notch, and the container was opened easily.

What is claimed is:
 1. A multilayer container comprising a multilayerstructure shaped to define a container portion having an opening and aflange portion surrounding the opening, said flange portion including aplanar portion arranged adjacent to said opening; said multilayeredstructure including a layer forming an inner surface layer of thecontainer portion and another layer contacting the inner surface layerand being laminated thereto; a notch extending into said inner surfacelayer and being located at an inner peripheral portion of said flangeportion, said notch being positioned inwardly of at least a part of theplanar portion so that upward peeling of the inner surface layer awayfrom said another layer allows at least a part of the inner surfacelayer in the planar portion of the flange portion of said multilayeredstructure to be separated from the another layer; at least a part of theplanar portion being adapted to be heat sealed to a lid member for thecontainer and to form a bond with said lid member exhibiting a peelstrength greater than the interlaminar strength of the inner surfacelayer and the another layer.
 2. A multilayer container according toclaim 1, wherein the layer structure of said inner surface layer andsaid layer contacting thereto is a combination of (A) a resin mixturelayer comprising a polypropylene base resin and a polyethylene baseresin and (B) a polyethylene layer.
 3. A multilayer container accordingto claim 2, wherein the weight ratio between said polypropylene baseresin and said polyethylene base resin is from 50:50 to 97:3.
 4. Amultilayer container according to claim 2, wherein said polyethylenelayer is a high density polyethylene.
 5. A multilayer containeraccording to claim 1, wherein said inner surface layer is a layer of apolyolefin resin, and said layer contacting to the inner surface layeris a layer of a metal.
 6. A multilayer container according to claim 1,wherein said notch is provided at a non-heat seal surface of said innerperipheral portion of said flange portion.
 7. A multilayer containeraccording to claim 1, wherein another notch is further provided to anouter layer at the outer peripheral portion of said flange portion.
 8. Amultilayer container according to claim 1, wherein a rib or curl portionis provided at an outer end of the flange portion, and a cut-off portionis provided at the rib or curl portion near the flange level.
 9. Amultilayer container according to claim 1, further comprising a lidmember covering the opening in the container portion and having a planarportion heat sealed to at least a part of the planar portion of theinner surface layer to provide a heat seal portion between the lidmember and the inner surface layer; the notch extending into said innersurface layer being located inwardly of said heat seal portion and saidmultilayered structure possessing an interlaminar strength smaller thana peeling strength exhibited by the heat seal portion between the lidmember and the inner surface layer so that during upward peeling of thelid member, a portion of the inner surface layer remains attached tosaid lid member and is separated from said another layer.
 10. Amultilayer container according to claim 9, wherein the notch is formedby pressing the lid member.
 11. A multilayer container according toclaim 10, wherein said notch and the heat seal portion are formedsimultaneously by pressing the lid member with the application of heat.12. A multilayer container according to claim 11, wherein pressing iseffected by a heat seal ring comprising a sealing member for effectingheat sealing and a ring projection member for forming a notch.
 13. Amultilayer container according to claim 9, wherein said notch is locatedat an innermost portion of said heat seal portion.
 14. A multilayercontainer comprising a multilayered structure shaped to define acontainer portion having an opening and a flange portion surrounding theopening, and a lid member covering the opening in the container portion;said flange portion including a planar portion arranged adjacent to saidopening; said multilayered structure including a layer forming an innersurface layer of the container portion and another layer contacting theinner surface layer and being laminated thereto; a notch extending intosaid inner surface layer and being located at an inner peripheralportion of said flange portion, said notch being positioned inwardly ofat least a part of the planar portion so that upward peeling of theinner surface layer away from said another layer allows at least a partof the inner surface layer in the planar portion of the flange portionof said multilayered structure to be separated from the another layer;said lid member having a planar portion heat-sealed to at least a partof the planar portion of the inner surface layer at a peripheral portionof the flange portion of the multilayered structure to provide a heatseal portion between the lid member and the inner surface layer, saidnotch being spaced from and located inwardly of said heat seal portion;said multilayered structure possessing an interlaminar strength smallerthan a peeling strength exhibited by the heat seal portion between thelid member and the inner surface layer so that during upward peeling ofthe lid member, a portion of the inner surface layer remains attached tosaid lid member and separates from said another layer.
 15. A multilayercontainer according to claim 14, wherein a space of 0.5 to 10 mm isprovided between said notch and an inner end of the heat seal portionprovided between said lid member and said inner surface layer; a peelingstrength from inside the covered container being substantially largerthan a peeling strength from outside required to separate the lid memberfrom the flange portion.
 16. A multilayer container according to claim15, wherein said space is from 1.5 to 5 mm.
 17. A multilayer containeraccording to claim 14, wherein said notch is a ring notch provided at anon-heat seal surface inside said heat seal portion.
 18. A multilayercontainer according to claim 14, wherein a heat unfusible layer isprovided on at least one surface of said flange portion and said lidmember inside the heat seal portion and said notch is a ring notchprovided inside said heat seal portion.
 19. A multilayer containeraccording to claim 14, wherein the layer structure of said inner surfacelayer and said another layer is a combination of (A) a resin mixturelayer comprising a polypropylene base resin and a polyethylene baseresin and (B) a polyethylene layer.
 20. A multilayer container accordingto claim 19, wherein the weight ratio between said polypropylene baseresin and said polyethylene base resin is from 50:50 to 97:3.
 21. Amultilayer container according to claim 19 wherein said polyethylenelayer is a high density polyethylene.
 22. A multilayer containeraccording to claim 14, wherein said inner surface layer is a layer of apolyolefin resin and said another layer is a layer of metal.
 23. Amultilayer container according to claim 14, wherein said notch isprovided at a non-heat seal surface of said inner surface layer at aninner peripheral portion of said flange portion.
 24. A multilayercontainer according to claim 14, wherein another notch is furtherprovided in an outer layer at an outer peripheral portion of said flangeportion.
 25. A multilayer container according to claim 14, wherein a ribor curl portion is provided at an outer end of the flange portion and acut-off portion is provided at the rib or curl portion near the flangelevel.